1. Field of the Invention
This invention relates to a gene and an adhesion molecule encoded by said gene, and in particular, relates to a gene encoding a polypeptide having pre-B cell growth-supporting ability, a vector containing said gene, transformants such as microorganisms or cells transformed by said vector and a method for producing the adhesion molecule having pre-B cell growth-supporting ability by using said gene.
The gene of the present invention encodes a novel adhesion molecule enhancing pre-B cell growth-supporting ability on the surface of bone marrow cells and synovial cells derived from patients with rheumatoid arthritis (RA) or multiple myeloma (MM). In the present invention, a homogeneous and purified adhesion molecule having pre-B cell growth-supporting ability can be produced in large quantities by transforming appropriate host cells with a suitable vector in which the gene of the present invention is inserted. Thus, according to the present invention, it becomes possible to identify multiple myeloma (MM) and rheumatoid arthritis (RA), and also prepare reagents for the clinical diagnosis thereof.
2. Description of the Prior Art
It has been reported that abnormalities of bone marrow cells are actually involved in the pathogenesis of B cell malignancies and autoimmune disease [Annu. Rev. Immunol., 9:243 (1991)].
Namely, multiple myeloma (MM) is a tumor which develops depending on microenvironment in the bone marrow and also a monoclonal plasmacytic tumor characterized by restricted growth in the bone marrow, and several studies have suggested that the oncogenic transformation of multiple myeloma (MM) occurred during the process of the differentiation and proliferation of early B cell development (pre-B cell) which is dependent on bone marrow stromal cells [J. Exp. Med., 150: 792 (1979), and Cancer Genet. Cytogenet, 17:13 (1985)].
Furthermore, the fact has been reported that bone marrow stromal cells were demonstrated to induce the growth of the precursor cells of multiple myeloma (MM) circulating in the peripheral blood of patients with multiple myeloma (MM) [Blood, 77:2688 (1991)].
Therefore, it is probable that bone marrow stromal cells provide stimulatory signals essential for the generation of multiple myeloma (MM).
In this regard, it has been known that the abnormal production of IL-6 may play a role in pathogenesis of rheumatoid arthritis (RA) [Eur. J. Immunol., 18:1797 (1988), and Clin. Immunol. Immunopathol., 62:S60 (1992)]. Besides, according to the results taking several murine autoimmune models into consideration reported in Eur. J. Immunol., 20:723 (1990) and Eur. J. Immunol., 21:63 (1991), it is suggested that the bone marrow derived from patients with rheumatoid arthritis (RA) is probably affected.
Namely, also in rheumatoid arthritis (RA), it is suggested that polyclonal B cell activation is probably caused by the bone marrow adjacent to an affected arthrosis.
The present inventors have engaged in extensive studies with a view to investigate the function of the bone marrow microenvironments in disorders causing abnormalities of B cells, and have reported that the pre-B cell growth-supporting ability of BM stromal cells derived from patients with RA or MM is enhanced in comparison with that of healthy donor-derived BM stromal cells, and that the direct cell-to-cell interaction of pre-B cells and stromal cells might play essential roles in this supporting ability. At the same time, the present inventors have obtained bone marrow specimens derived from patients with MM and RA after informed consent, and established novel stromal cell lines (RASV5-5, MMSV3-3) containing a molecule enhancing the growth of pre-B cells, on the basis of the speculation that there should be a surface molecule enhancing the growth of pre-B cells on the bone marrow stromal cells derived from patients with RA and MM. It has been suggested that the pre-B cell growth-supporting activity of these stromal cell lines is most likely caused by unknown adhesion molecules different from known Stem cell factors (SCF), ICAM-1, CD44, VCAM-1, LFA-1.alpha., LFA-1.beta., NCAM and ELAM-1 [J. Immunol., 149:4088 (1992)].
Therefore, the present inventors have prepared for a monoclonal antibody using the BM stromal cell line RASV5-5 having enhanced pre-B cell growth-supporting ability derived from patients with RA as an antigen for immunization, and obtained a monoclonal antibody RF3 responding to BM stromal cell lines derived from patients with RA and MM, and not responding to a stromal cell line NFSV1-1 derived from the human bone marrow having no pre-B cell growth-supporting ability.
Further, the present inventors have found that a monoclonal antibody yielded by the hybridoma SG2, which obtained from the immunized cell line SynSV6-14 of the synovial cell derived from patients with RA, responds to BM stromal cell line RASV5-5 derived from patients with RA, and does not respond to the stromal cell line NFSV1-1 derived from the human bone marrow having no pre-B cell growth-supporting ability.